The mechanisms underlying the formation of visual-motor associations, and the role of dopamine in this process, are topics of great importance in neuroscience. Derangements of this circuitry may play a role in Parkinson's Disease (PD) and learning disorders such as autism. There are numerous studies indicating that patients with PD suffer from learning deficits. In one such study, patients with PD were found to have impairments in sequence learning that were reversed with the administration of the dopamine precursor levodopa (Shohamy, D. et al., Behav Brain Res. 156:191-199, 2005). In support of the role of dopamine in learning, a recent study found that in normal human subjects, levodopa significantly enhanced the speed, overall success, and long-term retention of novel word learning in a dose-dependent manner (Knecht, S. et al., Ann Neurol. 56: 20-26, 2004). In addition, there is increasing evidence that striatal dysfunction may be an important component of autism. Volumetric MRI studies have suggested that there are differences in caudate size between normal and autistic children (Hollander, E. et al., Biol Psychiatry 58: 226-232, 2005). Other studies have suggested that autistic children may have increased serum antibodies to the caudate nucleus (Singh, V. K. & Rivas, W. H., Neurosci Lett. 355: 53-56, 2004), but the role of specific brain regions in learning such as the formation of visual-motor association remains unclear.